JPH0122141Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a measuring instrument using a clip type transformer.

In a measuring instrument using a clip-type transformer, accurate measurements cannot be made unless the divided ends of the core of the transformer are securely engaged in the measuring state.

The measuring device of the present invention utilizes a display that numerically displays the amount of electricity to be measured, and when the core split end is poorly engaged, the number on the display flashes to provide an alarm signal. It is.

FIG. 1 is a block diagram showing an embodiment of a measuring device according to the present invention. In the figure, CT ₁ is an injection transformer, and CT ₂ is a detection transformer. Transformer CT ₁ ,
CT ₂ each has a pair of semicircular cores CO ₁ and CO ₂
The cores CO 1 and CO 2 are arranged in an annular manner to form a closed magnetic path, and the cores CO ₁ and CO ₂ are arranged with one of the divided ends 11 as a fulcrum, or one of the cores is The other divided end 12 can be opened together with the divided end 11 portion. NP is injection coil, ND is detection coil, NC
are auxiliary coils, coils NP and NC are wound around cores CO ₁ and CO 2 of transformer CT ₁ , and coil ND is wound around cores CO 1 and CO ₂ of transformer CT 1.
It is wrapped around the cores CO ₁ and CO ₂ of CT ₂ . The OSC is an oscillator, and its oscillation frequency is selected to be a frequency ₂ that can be sufficiently distinguished from the frequency ₁ of the circuit current source SO so as not to be affected by the circuit current ie during measurement. RP is a resistive element, PA is a power amplifier,
The output of the oscillator OSC is amplified by the power amplifier PA via the resistance element RP, and then applied to the injection coil NP. RE ₁ is a rectifier amplifier circuit, LV is a level comparator, BPA is a frequency selection amplifier that passes only _two frequency components of the induced voltage in the coil ND obtained by the resistor RD, and RE ₂ is a rectifier amplifier for the output of BPA. AD is an analog-to-digital converter (hereinafter referred to as AD converter) that converts the output of the rectifier amplifier circuit RE ₂ into a digital signal, and DD converts the output of the AD converter into a BCD signal and converts the digit signal into a digital signal. Display drive circuit to output, DS is numeric display, D ₁ , D ₄ are display drivers, D ₂ , D ₃
is the decoder driver. The output BCD signal of the display drive circuit DD is applied to the display driver D ₁ and decoder drivers D ₂ and D ₃ , and the display DS is affected by the upper three digits by the outputs of D ₁ to _{D 3} given according to the digit signal. Displays the measured resistance Rx value numerically. display
As will be described later, the lowest digit of DS is designed to flash when divided end faces 11 and 12 of transformer CT ₁ are not engaged.

HO is a hold circuit, consisting of a switch SW, a voltage source +V, a resistor _R1 , and an AND gate AG.
The latch signal output by the AD converter is the switch SW
is off, the display drive circuit DD and the flip-flop FF C, which will be described later, are connected via the AND gate AG.
sent to the terminal. When the switch SW turns on, the latch signal is cut off by the AND gate AG.
The display drive circuit DD holds the output of the AD converter when the switch SW is turned on. FC is a flashing circuit, which is composed of a flip-flop FF, a multivibrator ML, an inverter IV, and the display driver _D4 . The D input terminal of the flip-flop FF is connected to the level comparator.
It is connected to the output terminal of LV, and the C input terminal is connected to the output terminal of AND gate AG. The multivibrator ML consists of a pair of NAND gates NG ₁ and NG ₂ , and its input end is connected to the Q terminal of the flip-flop FF. Output end is inverter
It is connected to the display driver D ₄ via IV, and the output of D ₄ is given to the least significant digit of the numeric display DS. . The multivibrator ML outputs a "1" level when the Q terminal of the flip-flop FF is "0", and this "1" level signal is inverted by the inverter IV and sent to the display driver.
Given to D ₄ . As a result, the lowest numeric value on the numeric display DS does not light up. When the Q output of the flip-flop FF is at the “1” level, the multivibrator ML is connected to the resistive element R ₂ (R ₃ ).
oscillates at a specific period determined by the capacitance of capacitor _C2 , and its oscillation output is given to the lowest digit of the display DS via inverter IV and display driver _D4 , thereby causing the lowest digit to flash. do.

The operation of the measuring instrument having such a configuration is as follows. A circuit current ie of frequency 1 flows through the connection line ₁ from a current source SO. The injection transformer CT ₁ and the detection transformer CT ₂ are respectively inserted into the connecting wire l from their split ends 12, and the connecting wire l is clipped. On the other hand, the output of the oscillator OSC is supplied as a voltage _e1 to the injection coil NP via the power amplifier PA. voltage e ₁
The cores CO ₁ and CO ₂ of transformer CT ₁ are energized by
A voltage e ₂ expressed by the following equation (1) is induced in the auxiliary coil NC.

e ₂ =NC/NPe ₁ (1) The voltage e ₂ is supplied to the power amplifier PA, thereby varying the voltage e ₁ applied to the injection coil NP.
In other words, the injection coil NP, auxiliary coil NC, and power amplifier PA induce a voltage e ₂ in the auxiliary coil NC.
A feedback loop is formed to vary the voltage e 1 so that the voltage e ₁ is always constant. Core CO ₁ , CO ₂ of transformer CT ₁
is excited by voltage e ₁ , so that the transformer
Since the connecting wire l, which corresponds to the secondary conductor of CT ₁ , has one turn, the frequency shown by the formula (2) below is
A voltage e _x of ₂ is injected.

e _x = 1/NP・e ₁ ...(2) The injection voltage e _x expressed by equation (2) increases the circuit network CL
A current ix expressed by ix=e _x /Rx (3) flows through. Detection coil ND of detection transformer CT ₂ by electromagnetic action with current ix
A current is induced in the coil, and this induced current causes the coil to
A voltage e ₃ expressed as e ₃ =ixRD/ND (4) is generated in the resistance element RD connected to the output terminal of ND. Detection transformer CT ₂
A voltage is also induced by the current ie at frequency ₁ by the current source SO, but the voltage of this frequency component is cut off by the selection amplifier BPA, and only the voltage e ₃ at frequency ₂ shown in equation (4) is induced. is a frequency selective amplifier
Extracted by BPA. Calculating Rx from equations (2) to (4), Rx=RD・e ₁ /ND・NP・e ₃ =RD・e ₂ /ND・NC・e ₃ ……
(5) becomes. In equation (5), RD, NP, ND, and NC are the values of the resistive element RD, the number of turns of the injection coil NP, detection coil ND, and auxiliary coil NC, which are constant, and e ₂ is also determined by the feedback loop described above. Since it is controlled to a constant value, if these are set as a constant k, equation (6) becomes Rx=k1/e ₃ (6). Rectifier circuit corresponding to the value of the resistance to be measured Rx
The output e ₄ of RE ₂ is converted into a digital signal by an AD converter. When the switch SW is off, the latch signal passes through the AND gate AG to the display drive circuit.
This latch signal causes the display drive circuit DD to sequentially capture the output of the AD converter.
The display drive circuit DD responds to the output of the AD converter.
The BCD signal is sent to the display driver D ₁ and decoder drivers D ₂ and D ₃ , and the output of this D ₁ , D ₂ , and D ₃ circuit is given to the upper three digits of the display DS according to the digit signal, and this The display DS numerically displays the value of the resistance to be measured Rx using the upper three digits. On the other hand, the hold circuit
The output of the AND gate AG in HO is applied to the C terminal of the flip-flop FF,
If the engagement between the split ends 11 and 12 of the clip transformer CT ₁ is less than a predetermined value, the level comparator
Since the output of LV is zero, the Q terminal of the FF circuit becomes a "0" level signal. This “0” level signal is input to the multivibrator ML, so ML outputs a “1” level signal, and this “1” level signal is inverted by the inverter IV and the display driver D Added to ₄ . As a result, the number of the lowest digit on the numeric display DI disappears. When the switch SW is turned on to hold the measured value, the latch signal is cut off by the AND gate AG, and the output of the AD converter is connected to the display drive circuit DD.
The value is held by the display DS.

Here, as described above, in the circuit shown in the figure, the auxiliary coil NC, the power amplifier PA, and the injection coil NP
A feedback loop is formed by the cores CO ₁ and CO ₂ of the injection transformer CT ₁ .
Control is performed so that the injection amount remains constant even if the air gap at the dividing ends 11 and 12 changes, but the limit of this control ability is determined by the power amplifier PA.
It is determined by the output limit of . For this reason, if dust or foreign matter gets caught in the divided ends 11 and 12 of the cores CO ₁ and CO ₂ and they do not mesh accurately, and the control system capacity exceeds the output limit value of the power amplifier PA, the induced voltage in the auxiliary coil NC will increase. e ₂ falls below a predetermined value, and therefore the injection voltage is no longer controlled to a constant value. If the injection voltage fluctuates, an indication error will occur as explained in equation (5). Therefore, the injection transformer
It is always necessary to detect whether the divided ends of CT ₁ are engaged within the control capability of the feedback loop, and if they are not engaged, the cause must be removed.

In the present invention, the induced voltage _e2 of the auxiliary coil NC provided in the injection transformer _CT1 is rectified by the rectifier amplifier circuit _RE1 , and then applied to the flip-flop FF via the level comparator LV. Therefore, if the threshold voltage of the level comparator LV is set, for example, near the limit value for feedback loop control, then the size of the air gap due to poor meshing of transformer CT ₁ will exceed the limit value for feedback loop control. voltage beyond e ₂
When exceeds the threshold of the level comparator LV,
This LV operates and its output is input to the D terminal of the flip-flop FF. In this case, when the switch SW is off, the latch signal passed through the AND gate AG is applied to the C terminal of the flip-flop FF. With the rise of this latch signal, the "1" level signal applied to the D terminal is transferred to the Q terminal. This "1" level signal is applied to multivibrator ML, and this ML circuit oscillates. The oscillation output of the multivibrator ML is applied to the display driver _D4 via the inverter IV, so that the least significant digit of the display DS flashes.

In this way, in the measuring instrument of the present invention, under normal measurement conditions, if the air gap between the split ends 11 and 12 exceeds a predetermined value due to poor meshing of the transformer CT ₁ , the number on the lowest digit of the display DS will be displayed. flashes, thereby warning that the data displayed by the display DS is not an accurate measurement.

Note that when the switch SW is turned on, the measured value is held as described above, but if the hold switch SW is turned on when CT ₁ is poorly engaged, the latch applied to the C terminal of the flip-flop FF is Since the signal is cut off, the flashing of the numbers on the display DS will continue unless the hold state is released by turning off the switch SW. This indicates that the held data is meaningless.
In this way, in this invention, if data is held with a misalignment, when the data is read, it is found that there is a misalignment, and the held data is expressed as meaningless. . The air gap of the detection transformer CT ₂ also affects the system as a whole, but the amount of influence is 1/1 of the effect in the air gap of the injection side transformer CT ₁ .
It is about 10, which poses no practical problem.

In the above-mentioned embodiments, the present invention was explained with respect to a measuring device for measuring resistance values, but it can also be used to measure not only resistance but also electric quantities such as current, voltage, or power using a clip-on transformer. Can be applied to measuring instruments that can be used. Further, in the above embodiment, the lowest digit number of the display is flashed, but not only the lowest digit number but also all digits may be flashed as an alarm signal. Other oscillation circuits may be used instead.

As explained above, according to the present invention, when the divided ends of the core of a clip-on transformer are not accurately engaged, the numbers on the display that displays the measured value will flash, and this will reduce the reliability. A high quality measuring instrument can be realized.

[Brief explanation of the drawing]

The figure is a block diagram of a measuring device according to an embodiment of the present invention. CT ₁ , CT ₂ ... Clip type transformer, LV ... Level comparator, ML ... Oscillation circuit, DS ...
Numerical display.

Claims (1)

[Claims for Utility Model Registration] A system comprising an injection coil and an auxiliary coil, and a feedback loop that supplies the output of an oscillator to the injection coil via a power amplifier and returns the induced voltage of the auxiliary coil to the power amplifier. A first clip-type transformer, a second clip-type transformer equipped with a detection coil, an analog-digital converter that converts the induced voltage of the detection coil into a digital signal, and the output of this analog-digital converter are displayed. A measuring device is provided with a numeric display that is applied via a drive circuit, and the amount of electricity to be measured is displayed numerically by clipping the conductor between the two clip type transformers, and the auxiliary coil is a level comparator that operates when an induced voltage is applied and the meshing size of the divided ends of the core of the first clip type transformer exceeds a predetermined value; and the output of this level comparator is transferred by the output of the analog-to-digital converter. A flashing circuit consisting of a flip-flop and a multivibrator that oscillates by the output of this flip-flop is provided, and the output of this flashing circuit is used to flash the lowest digit or all digits of the numeric display to issue an alarm. A clip-type measuring device that is characterized by a signal.